code: def test_pickle():
      import pickle
  
      for protocol in range(pickle.HIGHEST_PROTOCOL + 1):
          A = interface.LinearOperator((3, 3), matvec)
          s = pickle.dumps(A, protocol=protocol)
          B = pickle.loads(s)
  
          for k in A.__dict__:
              assert_equal(getattr(A, k), getattr(B, k))
  
imports: from functools import partial
  from itertools import product
  import operator
  from pytest import raises, warns
  from numpy.testing import assert_, assert_equal
  import numpy
  import scipy.sparse
  import scipy.sparse.linalg._interface
  from scipy.sparse._sputils import matrix
label_desc: Use image node_id 5 for calling a global function with example usage: test_pickle() without return types